Systems and methods for a predistortion linearizer with frequency compensation

ABSTRACT

An analog predistortion linearizer system with dynamic frequency compensation for automatically adjusting predistortion characteristics based on a detected frequency includes a frequency detector configured to generate at least one frequency detection signal in response to receiving an amplifier drive signal, the frequency detection signal including a frequency indicator that indicates the frequency of the amplifier drive signal. Moreover, the system also includes a controller communicatively coupled to the frequency detector and configured to generate a predistorter control signal in response to receiving the frequency detection signal from the frequency detector, and a predistorter communicatively coupled to i) the frequency detector and ii) the controller, the predistorter configured to generate a predistorted amplifier drive signal based on at least the predistorter control signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the nonprovisional application of provisionalapplication, Ser. No. 62/133,827, filed on Mar. 16, 2015, which isincorporated by reference in its entirety herein.

FIELD OF INVENTION

This disclosure generally relates to predistortion conditioning for apower amplifier, and more specifically, to a predistortion linearizerincludes frequency compensation in preconditioning a drive signal for apower amplifier.

BACKGROUND

Microwave and millimeter-wave communications systems are used in manyapplications, including satellite communications, terrestrialpoint-to-point communications, and backhaul communications for cellularnetworks. Typically, a communications transmitter includes a high poweramplifier to increase the power of the signal to levels adequate toreach a distant receiver with sufficient strength. It is important thatthese communications transmitters preserve the fidelity or the“linearity” of the communications signals to avoid unnecessarydistortion.

Typically, a high power amplifier will add some undesirable distortionto signals during the amplification process. For example, as the powerfor an input drive signal increases, an amplifier will amplify the drivesignal by a proportionate gain. However, when the power of the inputdrive signal reaches a certain level, the amplifier begins to becomesaturated and is no longer capable of amplifying the drive signal by aproportionate gain. In other words, as the amplifier becomes saturatedat these higher input power levels of the drive signal, the amplifierbegins to add saturation distortion to the amplified output. Thus, thehigh-power amplifier will not produce sufficient gain and adds amplitudedistortion to the output signal above a certain level of input drivepower. In addition, the phase of the output signal can also becomedistorted as the amplifier saturates which further compounds thesaturation distortion problem. This amplitude (also referred to asmagnitude) and phase distortion result in a loss of fidelity of theoutput signal, and will limit the capacity of the communications system.

Conventional amplifier designers have attempted to mitigate thisdistortion characteristic of the amplifier by coupling a predistorterdevice to the amplifier. The predistorter attempts to counteract thedistortion characteristics of the amplifier by preconditioning the drivesignal before amplification. For example, a predistorter may add aninverse gain magnitude and inverse gain phase saturation distortioncharacteristics to the drive signal before amplification. Thus, when thepredistorted drive signal is amplified, the inverse magnitude andinverse phase saturation distortion characteristics will counteract thesaturation magnitude and phase distortion added during amplification. Asa result, the operating power levels of an amplifier may be extendedinto much higher power levels without exhibiting much distortion. Thesedevices are said to extend the linear output power of the high poweramplifier. The benefits of using linearization techniques to extend theuseful power of a high-power amplifier are well documented.

However, many amplification applications require the use of more thanone frequency, and some applications may even require the use of anentire broad frequency band. Generally, power amplifiers exhibitdifferent saturation distortion characteristics for drive signals ofdifferent frequencies. In other words, the amplifier distortioncharacteristics of a particular amplifier will change over the frequencyof a band of interest. This difference in saturation distortioncharacteristics of an amplifier becomes even more pronounced forwideband applications that require a greater range in frequencies in anoperating bandwidth. It is often quite difficult to design aconventional predistorter to counteract the amplifier's gain magnitudeand phase saturation over a wide frequency band, especially if theamplifier's gain magnitude and phase saturation vary significantly overthis band. As a result, while conventional predistorters may help extendthe operating range for an amplifier at one particular frequency, thoseconventional predistorters are often inadequate for applications thatrequire amplification for an entire band of frequencies.

SUMMARY

An analog predistortion linearizer system with dynamic frequencycompensation for automatically adjusting predistortion characteristicsbased on a detected frequency includes a frequency detector configuredto generate at least one frequency detection signal in response toreceiving an amplifier drive signal, the frequency detection signalincluding a frequency indicator that indicates the frequency of theamplifier drive signal. Moreover, the system also includes a controllercommunicatively coupled to the frequency detector and configured togenerate a predistorter control signal in response to receiving thefrequency detection signal from the frequency detector, and apredistorter communicatively coupled to i) the frequency detector andii) the controller, the predistorter configured to generate apredistorted amplifier drive signal based on at least the predistortercontrol signal.

According to one embodiment, an analog predistortion linearizer systemwith dynamic frequency compensation automatically adjusts predistortioncharacteristics based on a detected frequency. The system includes afrequency detector configured to generate at least one frequencydetection signal in response to receiving an amplifier drive signal. Thefrequency detection signal includes an frequency indicator thatindicates a frequency of the amplifier drive signal. A controllercommunicatively is coupled to the frequency detector and is configuredto generate at least one predistorter control signal in response toreceiving the at least one frequency detection signal from the frequencydetector. A predistorter communicatively coupled to the frequencydetector and the controller. The predistorter is configured to generatea predistorted amplifier drive signal based on at least the predistortercontrol signal.

According to another embodiment, a processor-executable methodautomatically adjusts predistortion characteristics of a radio frequencysignal includes receiving a radio frequency signal. The method detects afrequency value in response to the receiving. The method furtherincludes generating a predistortion control signal in response to thedetected frequency value. The method also generates predistortion signalto the radio frequency signal such that the generated predistortionsignal counteracts a gain magnitude and phase distortion of an amplifierwhen processing the radio frequency signal.

A predistortion linearizer apparatus with dynamic frequency compensationautomatically adjusts predistortion characteristics based on a detectedfrequency. A predistorter for receiving a drive signal. A frequencydetector is communicatively coupled to the predistorter. Thepredistorter communicates the received drive signal with the frequencydetector. The frequency detector generates a frequency detection signalin response to the received drive signal. The frequency detection signalincludes a frequency indicator that indicates a frequency of the drivesignal. A controller is communicatively coupled to the frequencydetector and the predistorter. The controller generates a predistortercontrol signal in response to receiving the at least one frequencydetection signal from the frequency detector. The apparatus furtherincludes the predistorter generating a predistorted drive signal basedon the predistorter control signal.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 depicts a gain magnitude distortion response graph and a gainphase distortion response graph for a drive signal being amplified overa range of input power levels according to prior art.

FIG. 2 depicts a gain magnitude and phase distortion response graph fora predistortion linearizer configured to substantially counteract thegain and phase distortion response of an amplifier according to priorart.

FIG. 3 depicts a gain magnitude distortion response graph and a gainphase distortion response graph for a drive signal being amplified overa range of input power levels at two different operating frequenciesaccording to one embodiment of the invention.

FIGS. 4a and 4b illustrate a block diagram for an exemplarypredistortion linearizer system that includes frequency compensationaccording to one embodiment of the invention.

FIGS. 5a and 5b depict prior art examples of different typespredistortion linearizers.

FIGS. 6a, 6b and 6c illustrate prior art examples of different types offrequency detection networks.

FIG. 7 illustrates an exemplary circuit board layout for a predistortionlinearizer system with a frequency detection module and a predistortionlinearizer.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION

FIG. 1 shows a typical amplifier's gain magnitude saturation curve 101and gain phase saturation curve 102 as a function of input poweraccording to prior art. As has been discussed previously, as the inputpower increases, the amplifier's gain magnitude and phase begin tochange as the amplifier saturates. This is true for any high-poweramplifier, including both vacuum-tube amplifiers as well as solid-stateamplifiers. FIG. 1 shows the amplifier gain magnitude decreasing withincreasing drive 101, which is the usual case. Some amplifiers, however,may exhibit behavior where the gain magnitude actually increases over acertain range of input powers, before ultimately decreasing. FIG. 1 alsoshows that the phase of the amplifier's gain decreasing with increasingdrive 102, but it should be noted that this phase response is notuniversal. Some amplifiers may show phase reduction with increasingdrive, while others may show a phase increase with increasing drive,while other amplifiers may show both behaviors.

FIG. 2 illustrates the concept of predistortion according to prior art.A predistorter attempts to correct the inevitable magnitude and phasedistortion introduced by a high power amplifier by intentionallypre-distorting the signal input to the amplifier with essentiallyopposite characteristics. In this example, the predistorter's gainmagnitude curve 103 has an opposite shape to the amplifier's gainmagnitude distortion curve 101: while the magnitude of the amplifiergain decreases with increasing power, the magnitude of the predistortergain increases with increasing power. These two effects will effectivecancel each other out, resulting in a gain magnitude that is essentiallyconstant over a wide range of power levels. The system's gain amplitudeis said to have been “linearized.” An identical approach can be appliedto linearize the gain phase saturation. In this example, thepredistorter's gain phase curve 104 has an opposite shape to theamplifier's gain phase distortion curve 102. Again, in this illustrativeexample the phase of the predistorter gain increases with power tocounteract the decreasing phase of the amplifier gain, but differentcharacteristics can exist.

FIG. 2 also shows near ideal predistortion, but it is important tostress that these amplifier distortion curves 101,102 and predistorterdistortion curves 103, 104 are shown at a single frequency of operation.Real communications systems have to operate of a band of frequencies,and this band can be quite wide: spanning several octaves or decades.Although the bandwidth of a signal passing through the amplifier may bequite narrow at any one instant of time (the instantaneous bandwidth),the amplifier must be able to linearly amplify any such signal orsignals existing in a wide bandwidth. The saturation characteristics ofa high-power amplifier and the distortion characteristics of apredistortion linearizer may change considerably over this widebandwidth. This is illustrated in FIG. 3, which shows a representativeamplifier's gain magnitude saturation curve at two different frequenciesin the band 101, 111. Note that the amplifier's gain magnitudesaturation at frequency “B” 111 occurs at higher input power levels thanthe amplifier's gain magnitude saturation at frequency “A” 101. Theamplifier's gain phase saturation curves at the two frequencies aremarkedly different. The amplifier's gain phase at frequency “A” 102decreases with increasing input power, whereas the gain phase atfrequency “B” 112 increases with increasing input power.

With FIG. 3 in mind, one skilled in the art would appreciate howdesigning a predistorter to optimally correct the amplifier's distortioncharacteristics at frequency “A” (e.g. a predistorter having acharacteristic like the one illustrated in FIG. 2) would result in asystem that does not work well at frequency “B”. That is, thepredistorter would have a gain phase characteristic that is increasingwith power (to counteract the amplifier's decreasing phase at frequency“A”), but this would result in actually making the total system's phasedistortion worse at frequency “B” (because the linearizer's phase andthe amplifier's phase are both increasing with power at this frequency).The result is that a designer of a predistortion linearizer faces adifficult task, in trying to optimally align the linearizer's gainmagnitude and phase to counteract the amplifier's gain magnitude andphase not only over a wide range of power levels, but a wide range offrequencies as well. This balancing act can be difficult to achieve, andthe designer will often have to come up with a compromise solution thatworks only marginally well across the frequency band.

Embodiments of the invention disclosed herein solve this challenge byintroducing dynamic frequency compensation to improve the linearoperating power of an amplifier over a bandwidth of frequencies. Thepredistortion linearizer system may receive an input drive signalintended for a high power amplifier and condition the drive signal forthe high power amplifier based on at least a detected frequency of thedrive signal. For example, the predistortion linearizer system mayinclude a frequency detector that determines a frequency of a receivedinput drive signal and provides the detected frequency value to acontroller. In response to receiving the frequency value, the controllermay determine predistorter control signal that indicates a gainamplitude and phase predistortion characteristic for the amplifier atthe particular detected frequency. In response to the predistorterreceiving the predistorter control signal, the predistorter mayprecondition the drive signal to exhibit the inverse of the gainamplitude and phase predistortion characteristic for the amplifier. As aresult, when the amplifier amplifies the preconditioned drive signal,the distortion characteristics for the amplifier at the detectedfrequency are equalized, and the operating power level of the amplifieris extended. Advantageously, the predistortion linearizer system withfrequency compensation allows a high power amplifier to be optimizedover an entire operating bandwidth without compromising the performanceof one particular frequency or band over another frequency or bandwithin the operating bandwidth.

As illustrated in FIG. 4a , an exemplary predistortion linearizer system400 with dynamic frequency compensation may include a frequency detector420 that is communicatively coupled with an analog predistorter 410 anda controller 430, and in turn, the controller 430 may be communicativelycoupled with the predistorter. Although the frequency detector 420, asshown in FIG. 4a , receives the input drive signal 440, the analogpredistorter may alternatively receive the drive signal before providingthe signal to the frequency detector, as is illustrated in FIG. 4b .Therefore, it is to be understood that embodiments of the inventionenable the communications between the frequency detector 420 and thepredistorter 410 without being limited to the direction of the signalflow between these two devices. For example, the frequency detector 420may detect the drive signal frequency and then provide the drive signalto the predistorter 410, or alternatively, the frequency detector 420may receive the preconditioned drive signal from the predistorter 410and then detect that preconditioned drive signal frequency. The orderingof the predistorter 410 and the frequency detector 420 is therefore notimportant to the overall functioning of the system and FIGS. 4a and 4bshowing the directional arrows are for illustration purposes and notlimiting embodiments of the invention. Regardless of the predistortionsystem configuration, the frequency detector 420 may detect thefrequency substantially maintaining or without substantially changingthe characteristics of the drive signal. The system works together totune or optimize the analog predistorter to best correct the magnitudeand phase nonlinearities of a subsequent amplifier based on thefrequency of the signal.

Still referencing FIG. 4a , the analog predistorter 410 accepts a radiofrequency RF signal at its input 430, and adds the suitable predistortergain amplitude and phase distortion characteristics necessary tocounteract the subsequent amplifier's gain magnitude and phasedistortion. The predistorter's gain magnitude and phase characteristicscan be adjusted or “tuned” through one or more predistorter controlsignals 415.

There are many examples of how the analog predistorter 410 may beimplemented. FIGS. 5a and 5b show two illustrative examples. FIG. 5ashows a popular approach, wherein the signal at the input port 430 isdivided and directed along two separate paths: a linear path 500 and anonlinear path 510. The signals are then recombined with appropriatephase shifts and attenuation to achieve a desired predistorter magnitudeand phase distortion This approach is known. In this illustration, two90-degree hybrids 520, 521 are used to split the signal into the linearand nonlinear path. The nonlinear path contains a nonlinear element 510.The linear path may contain variable phase shifters 502 and variableattenuators 501. These variable components may be controlled by one ormore control signals 425. Adjusting these control signals will in turnchange the shape of the predistorter's gain magnitude and phasedistortion characteristics, and these signals can be used to optimizethe performance over the specified range of frequencies.

Another example of an analog predistortion linearizer is shown in FIG.5b . In this example, a nonlinear element is inserted into a circuitwith a pi-network topology in order to achieve the desired necessarypredistorter gain magnitude and phase distortion. In this example, forillustrative purposes only, the nonlinear element is a FET 620, and thepi-network consists of three resistors 610, 611, 612 and a variablecapacitor 615 bridging the central resistor 610. Control signals 425 areused to control both the FET 620 and the variable capacitor 615.Adjusting these control signals will in turn change the shape of thepredistorter's gain magnitude and phase distortion characteristics, andthese signals can be used to optimize the performance over the specifiedrange of frequencies.

It is important to stress that the analog predistorters shown in FIGS.5a and 5b are for illustrative purposes only. One skilled in the art mayrecognize that there are many possible analog predistortion linearizerarchitectures that would be suitable to be used with the frequencycompensation taught herein.

Looking back again to FIG. 4a , the frequency detector operates byreceiving an input radio frequency RF signal at its input 421 andpassing this RF signal to its output 422 substantially maintaining orwithout substantially changing the characteristics of this RF signal.For example, the frequency detector does not, in general, add modulationor filtering to the RF signal, nor does it, in general, add anydistortion or pre-distortion. The frequency detector generates adetected frequency signal or signal based on the frequency of the RFsignal.

There are many ways that the frequency detector can be implemented. Forexample, the frequency detector may determine the frequency of the drivesignal utilizing a frequency discriminator (e.g., a Foster-Seeleydiscriminator, a ratio discriminator, etc.), a phase-locked loop (PLL),or any other suitable manner of determining the frequency of the drivesignal. Alternatively, the frequency detector may include adownconverter that may downconvert the drive signal to a lowerintermediate frequency. In this alternative example, the intermediatefrequency may be digitized with an analog-to-digital converter fordetermining the frequency using one or more digital signal processingmethods. FIGS. 6a-6c show three well-known methods. FIG. 6a shows afrequency discriminator based on a slope detection circuit. A coupler701 is used to sample a portion of the RF signal. This sampled portionpasses through a steeply sloping filter 710 and then a power detector711. The strength of the signal from the power detector will indicatethe frequency of the RF signal. In this example, the slope detectorpasses lower frequencies and attenuates higher frequencies, so theoutput of the detector will be inversely proportional to the RF signalfrequency. FIG. 6b shows a refinement of this approach, where thecoupler 701 samples a portion of the RF signal and passes it through twofilters: a low-pass filter 714 and a high-pass filter 713, each beingfollowed by a subsequent detector 711. By comparing the relativestrengths of these two detected signals 415, one should be able todetermine the frequency of operation. Finally, FIG. 6c shows a thirdpossible architecture for the frequency detector. In this case, thesampled portion of the RF signal is processed by a phase-locked-loopcircuit, consisting of a phase detector 716, a loop filter 717 and avoltage controlled oscillator 718. The voltage controlling the voltagecontrolled oscillator will contain the information necessary todetermine the RF operating frequency. Again, it is important to stressthat the frequency detectors shown in FIG. 6 are for illustrativepurposes only. One skilled in the art may recognize that there are manypossible frequency detector architectures that would be suitable to beused with the frequency compensation taught herein.

After the frequency detector determines a value of the instantaneousfrequency of the drive signal, the frequency detector may provide thefrequency value as an analog or digital signal to the controller, asshown in FIGS. 4a-4b . In response to receiving the frequency value, thecontroller may determine one or more desired predistorter control signalor signals based on the received frequency value. For example, thecontroller may include an operational amplifier (i.e., op-amp) circuitthat includes one or more op-amps that may process the received analogbased frequency value and, in turn, may generate the properpredistortion signal(s) for the predistorter. Alternatively, thecontroller may include a microcontroller that includes one or moreprocessors and a memory in which the one or more processors may executeinstructions stored on the memory.

In continuing this alternative example, the microcontroller may receivethe digitized frequency value (or the microcontroller may be combinedwith the frequency detector to determine the digitized frequency)utilize a programmable lookup table to determine a predistorter controlsignal. This programmable lookup table may be generated during aninitial alignment and/or calibration setup phase. The lookup table, inaddition to a detected frequency value, may incorporate additionalfactors or variables, such as temperature, for example, to furtherrefine the determination and subsequent generation of one or morepredistortion control signals. Regardless of the manner implemented, thecontroller may convert the digital result of the lookup table into ananalog signal, using a digital-to-analog converter, to generate thepredistorter control signal.

Certain embodiments are described herein as including logic or a numberof components, modules, or mechanisms. Modules may constitute eithersoftware modules (e.g., code embodied on a machine-readable medium or ina transmission signal) or hardware modules. A hardware module istangible unit capable of performing certain operations and may beconfigured or arranged in a certain manner. In example embodiments, oneor more computer systems (e.g., a standalone, client or server computersystem) or one or more hardware modules of a computer system (e.g., aprocessor or a group of processors) may be configured by software (e.g.,an application or application portion) as a hardware module thatoperates to perform certain operations as described herein.

In various embodiments, a hardware module may be implementedmechanically or electronically. For example, a hardware module maycomprise dedicated circuitry or logic that is permanently configured(e.g., as a special-purpose processor, such as a field programmable gatearray (FPGA) or an application-specific integrated circuit (ASIC)) toperform certain operations. A hardware module may also compriseprogrammable logic or circuitry (e.g., as encompassed within ageneral-purpose processor or other programmable processor) that istemporarily configured by software to perform certain operations. Itwill be appreciated that the decision to implement a hardware modulemechanically, in dedicated and permanently configured circuitry, or intemporarily configured circuitry (e.g., configured by software) may bedriven by cost and time considerations.

Similarly, the methods or routines described herein may be at leastpartially processor-implemented. For example, at least some of theoperations of a method may be performed by one or more processors orprocessor-implemented hardware modules. The performance of certain ofthe operations may be distributed among the one or more processors, notonly residing within a single machine, but deployed across a number ofmachines. In some example embodiments, the processor or processors maybe located in a single location (e.g., within a home environment, anoffice environment or as a server farm), while in other embodiments theprocessors may be distributed across a number of locations.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses of a machine (e.g., a computer) that manipulates or transformsdata represented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

Still further, the figures depict preferred embodiments of apredistortion linearizer system for purposes of illustration only. Oneskilled in the art will readily recognize from the foregoing discussionthat alternative embodiments of the structures and methods illustratedherein may be employed without departing from the principles describedherein. Thus, upon reading this disclosure, those of skill in the artwill appreciate still additional alternative structural and functionaldesigns for a predistortion linearizer system through the disclosedprinciples herein. Thus, while particular embodiments and applicationshave been illustrated and described, it is to be understood that thedisclosed embodiments are not limited to the precise construction andcomponents disclosed herein. Various modifications, changes andvariations, which will be apparent to those skilled in the art, may bemade in the arrangement, operation and details of the method andapparatus disclosed herein without departing from the spirit and scopedefined in the appended claims.

What is claimed is:
 1. An analog predistortion linearizer system withdynamic frequency compensation for automatically adjusting predistortioncharacteristics based on a detected frequency, the system comprising: afrequency detector generating at least one frequency detection signal inresponse to receiving an amplifier drive signal, the at least onefrequency detection signal including a frequency indicator thatindicates a frequency of the amplifier drive signal, said at least onefrequency detection signal comprising an analog signal or a digitalsignal; a controller communicatively coupled to the frequency detectorand generating at least one predistorter control signal in response toreceiving the at least one frequency detection signal from the frequencydetector; and an analog predistorter communicatively coupled to i) thefrequency detector and ii) the controller, the analog predistortergenerating a predistorted amplifier drive signal based on the at leastone predistorter control signal, wherein said controller comprising acircuit for processing the received analog signal and for generating aproper predistortion signal for the analog predistorter.
 2. The analogpredistortion linearizer system of claim 1, wherein the predistortedamplifier drive signal comprises gain amplitude and phase distortioncharacteristics to counteract gain amplitude and phase distortionproperty of an amplifier.
 3. The analog predistortion linearizer systemof claim 1, wherein the frequency detector communicates the amplifierdriver signal with the predistorter while substantially maintainingcharacteristics of the signal.
 4. A processor-executable method forautomatically adjusting predistortion characteristics of a radiofrequency signal comprising: receiving, via a frequency detector, theradio frequency signal; detecting, via the frequency detector, afrequency value in response to the receiving; generating, via thefrequency detector, at least one frequency detection signal in responseto detecting, said at least one frequency detection signal comprising ananalog signal or a digital signal; generating, via a controller, apredistortion control signal in response to the detected frequencyvalue; and generating, via an analog predistorter, a predistortedamplifier drive signal to the radio frequency signal such that thegenerated predistorted amplifier drive signal counteracts a gainamplitude and phase distortion of an amplifier when processing the radiofrequency signal, wherein said controller comprises a circuit forprocessing the received analog signal and for generating a properpredistortion signal for the analog predistorter.
 5. Theprocessor-executable method of claim 4, wherein the predistortedamplifier drive signal comprises gain amplitude and phase distortioncharacteristics to counteract the gain amplitude and phase distortionproperties of the amplifier.
 6. The processor-executable method of claim4, further comprising communicating, via the frequency detector, thepredistorted amplifier driver signal with the analog predistorter whilesubstantially maintaining characteristics of the radio frequency signal.7. The processor-executable method of claim 4, wherein detectingcomprises detecting the frequency value.
 8. The processor-executablemethod of claim 4, wherein detecting comprises detecting the frequencyvalue.
 9. An analog predistortion linearizer apparatus with dynamicfrequency compensation for automatically adjusting predistortioncharacteristics based on a detected frequency, the apparatus comprising:an analog predistorter for receiving a drive signal; a frequencydetector communicatively coupled to the analog predistorter, wherein theanalog predistorter communicates the received drive signal with thefrequency detector; wherein the frequency detector generates a frequencydetection signal in response to the received drive signal, the frequencydetection signal including a frequency indicator that indicates afrequency of the drive signal, said at least one frequency detectionsignal comprising an analog signal or a digital signal; a controllercommunicatively coupled to the frequency detector and the analogpredistorter, said controller generating a predistorter control signalin response to receiving the at least one frequency detection signalfrom the frequency detector; and wherein the analog predistortergenerates a predistorted drive signal based on the predistorter controlsignal, and wherein said controller processes the received analog signaland for generating a proper predistortion signal for the analogpredistorter.
 10. The analog predistortion linearizer apparatus of claim9, wherein the predistorted drive signal comprises gain amplitude andphase distortion characteristics to counteract gain amplitude and phasedistortion property of an amplifier.
 11. The analog predistortionlinearizer apparatus of claim 9, wherein the frequency detector directsthe driver signal while substantially maintaining characteristics of thedrive signal.
 12. The analog predistortion linearizer apparatus of claim9, wherein the controller comprises a processor and a memory, whereinthe controller processes the digital signal.
 13. The analogpredistortion linearizer apparatus of claim 12, wherein the controllerdigitizes the frequency detection signal and to store data associatedwith the frequency detection signal in a programmable lookup table todetermine the predistorter control signal.